Multiple sclerosis (MS) is an inflammatory disease of the brain and spinal cord characterized by recurrent foci of inflammation that lead to destruction of the myelin sheath. In many areas, nerve fibers are also damaged. Inflammatory activity in MS patients tends to be highest in the initial phase of disease.
Data have demonstrated that irreversible axonal loss occurs early in the course of MS. Transected axons fail to regenerate in the central nervous system (CNS); and therefore, early treatment aimed at suppressing MS lesion formation is of significant importance. As early as disease onset, axons are transected in lesions with active inflammation (Trapp et al. (1998) N Engl J Med 338: 278-285; Bjartmar et al. (2001) Curr Opin Neurol 14: 271-278; Ferguson et al. (1997) Brain 120: 393-399). The degree of demyelination is related to the degree of inflammation and the exposure of demyelinated axons to the inflammatory environment, as well as non-inflammatory mediators (Trapp et al. (1998) N Engl J Med 338: 278-285; Kornek et al. (2000) Am J Pathol 157: 267-276; Bitsch et al. (2000) Brain 123: 1174-1183). There is also destruction of oligodendrocytes with impaired remyelination in demyelinating lesions (Peterson et al. (2002) J Neuropathol Exp Neurol 61: 539-546; Chang et al. (2002) N Engl J Med 346: 165-173). The loss of oligodendrocytes leads to a reduction in the capacity to re-myelinate and may result in the loss of trophic factors that support neurons and axons (Bjartmar et al. (1999) J Neurocytol 28: 383-395).
MS-mediated damage to the brain and spinal cord causes not only physical disabilities, but also significant cognitive impairment. Despite the significant impact that cognitive impairments have on the overall disability and quality of life of MS patients, adequate tools for the assessment of MS-associated cognitive impairments are needed. Current test batteries for assessment of cognitive impairment often require a panel of lengthy, cumbersome tests many of which are not pertinent to the disease itself and that require administration and interpretation by trained neuropsychologists.
Therefore, there is a need to establish a practical and valid cognitive measurement tool for use in MS patient evaluation, which are not only tailored to assess the cognitive domains affected by MS, but are also efficient, and easily administered with cross-cultural utility.